Supply circuit



suPPIJY CIRCUIT Filed May 22. 1930 INVENTOR g RUDOLF GURTLER w-u L/ ATTORNEY Patented June 13, 1933 UNITED STATES RUDOLF G'U'RTLER, OF BERLIN, GERMANY, ASSIGNOR T0 TELEFUNKEN GESELLSCHAFT FUR DRAHTLOSE TELEGRAPHIE M. B. H.,

GERMANY OF BERLIN, GERMANY, A CORPORATION OF SUPPLY CIRCUIT Application filed May 22, 1930, Serial No. 454,816, and in Germany June 1, 1929.

When the tubes of a power transmitter are heated with current of medium or high frequency (say, 10000 cycles ps), then the lead from the heating (filament-supply) transformer to the tubes must present a minimum of inductance in order that the inductive fall of potential due to the large heating or filament current and the high frequency may not become unduly great.

This requirement, as known from the prior art, is satisfied most closely by using as the supply leads co-aXial tubes or parallel bands or strips separated only by a thin layer of insulation such as mica. This latter design is most customarily used.

If a plurality of transmitter tubes or banks or transmitter tubes are to be supplied with filament current from one and the same filament supply transformer, it is necessary that each of such leads should present the same inductance fall of potential in order that the heating potential may be the same throughout all of the tubes. To accomplish this is an object of the present invention and it is accomplished, if the filament supply transformer is not mounted symmetrically with relation to the tubes or banks of tubes, by inserting impedances, preferably high inductances in the shorter leads. According to this invention increased inductance is effected by increasing the distance between the bands of strips conducting the heating energy.

The present invention is more fully described in connection with the accompanying drawing, in which Figure 1 dia rammatically illustrates vacuum tubes, in, or example, a radio transmitter, located unsymmetrically with reference to a source of heating current for the cathodes of the tubes whereby normally, due to the unequal inductances presented, unequal cathode heating current distribution follows,

Figures 2, 3 and 4 indicate variometer arrangements for varying the impedance and preferably the inductance between each tube and the source whereby predetermined usually equal, cathode energizing currents may be obtained.

ensues.

Figure 5 is a fastening arrangement useful in connection with the apparatus disclosed in Figures 2, 3 and 4, and

Figures 6 and 7 illustrate another variometer arrangement adapted to be used in the present scheme for maintaining predetermined current distribution to the oathodes of a bank of tubes.

Turning to Figure 1, a source of alternating current 2is shown supplying feeders 3 through the intermediary of transformer 4 with current for supplying cathode heating energy to electron discharge devices 6, 8, whose circuits have been omitted for the sake of simplicity. Because of the inductance of the portion of the feeder line 3 included between points Y, the voltage drop therein will preclude tube 8 from obtaining the same heating current that tube 6 is supplied with, giving rise to undesirable effects in the transmitter. To remedy this defect, the impedance and preferably the inductance of branch lines a, a, feeding the'cathode of tube 6 isincreased by increasing the spacing of the branch connections a, c, referred to.

The defect referred to is, of course, due to the fact that the tube 6 and 8 forming part of the bank of tubes usually used in a transmitter, are unsymmetrically arranged with 'leads to'tubes 8 and the succeeding tubes would be altered in inductance in order to maintain predetermined heating currents.

Not only may the inductance be varied to obtain equal heating currents, but, in the event that tubes are used which have unequal electron emissions, the voltages applied to the tubes may be altered in the manner described so that equal emission vA more advantageous scheme is to have recourse to a variometer placed at point Q,

for example, of a simple mechanical construction and allowing of correct adjustment for the requisite inductance- This variometer is schematically illustrated in Figs. 2,

3 and 4. One of the conductors of heating current or bands a is bent step-fashion, and so is the insulation layer 6. The other band or strip a is broken off at the points a: where the step begins. A step-shaped piece of 5 band or strip (Z is laid against the band 0.

Then, by shifting (Z the rectangular or parallelogram shaped winding surface (see Figs. 3 and l, respectively) is altered, vary ing the spacing between the conductor portions between points a; of the heating cur rent leads is altered.

The assembling of the constituent parts of the variometer can be effected in various Ways and means, for instance:

(1) The bands have holes at different places through which screw bolts enveloped by an insulating bush are pushed. Here the inductance as will be seen can be changed by steps by suitable hole spacing.

(2) Band piece (Z at its two ends is pressed against the band 0 by pairs of Pertinax or insulating plates 6, e, by the agency of screws disposed in axes f f (Fig. 3).

If prior to the starting of the transmitter the correct inductance had been? adjusted, then (Z can be soldered together with 0 in the final position if desired.

In the case of concentric pipes or tubes a variometer can be constructed as shown in Figs. (3 and 7 in such a way that the tubing is semicircularly broken at a given point. The outer clip a is half cut open so that it assumes a trough-shaped cross-sectional form. The inner clip 0 may keep the sectional form of the tube. An increase in inductance then is effected by tuning the clips a and Z) with reference to each other, as shown for example, in Fig. 7 for the section taken on line mn, Fig. 6.

4.0 I claim 1. In electrical apparatus of the character described, a plurality of tubes having cathodes adapted to be energized by alternati ing current, a source of alternating current, connections between the source and the tubes and adjustable inductive means in the connection leads of each tube for varying the effective inductance between each tube cathode and the source until the predetermined current distribution desired is obtained.

2. In electrical apparatus of the character described, a plurality of tubes having cathodes adapted to be energized by alternating current, a source of alternating ourrent, connections between the source and the tube cathodes and variometer means in the connections for varying the effective inductance interposed between each tube cathode and the source of heating current in order to control, in predetermined fashion, the

heating current supplied to each tube.

RUDOLF' GURTLER. 

